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perf machine: Factor out machine__idle_thread()

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Factor out machine__idle_thread() so it can be re-used for guest machines.

A thread is needed to find executable code, even for the guest kernel. To
avoid possible future pid number conflicts, the idle thread can be used.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Andi Kleen <ak@linux.intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: https://lore.kernel.org/r/20210218095801.19576-7-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Adrian Hunter
2021-02-18 11:57:56 +02:00
committed by Arnaldo Carvalho de Melo
parent fcda5ff711
commit 3035cb6cbd
3 changed files with 22 additions and 22 deletions
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18
tools/perf/util/machine.c
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@@ -598,6 +598,24 @@ struct thread *machine__find_thread(struct machine *machine, pid_t pid,
return th;
}
/*
* Threads are identified by pid and tid, and the idle task has pid == tid == 0.
* So here a single thread is created for that, but actually there is a separate
* idle task per cpu, so there should be one 'struct thread' per cpu, but there
* is only 1. That causes problems for some tools, requiring workarounds. For
* example get_idle_thread() in builtin-sched.c, or thread_stack__per_cpu().
*/
struct thread *machine__idle_thread(struct machine *machine)
{
struct thread *thread = machine__findnew_thread(machine, 0, 0);
if (!thread || thread__set_comm(thread, "swapper", 0) ||
thread__set_namespaces(thread, 0, NULL))
pr_err("problem inserting idle task for machine pid %d\n", machine->pid);
return thread;
}
struct comm *machine__thread_exec_comm(struct machine *machine,
struct thread *thread)
{